Apex domains cannot have CNAME records.
Question and response
Question
dig claro.com.py. NS
Answer
claro.com.py. 5 NS ns2.claro.com.ar.
claro.com.py. 5 NS ns1.claro.com.ar.
Authority
The response has no authority records.
Additional
ns1.claro.com.ar. 5 A 170.51.242.140
ns2.claro.com.ar. 5 A 186.12.254.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0